Abstract

Compton scattering hard X‐ray source for 10–80 keV are under construction using the X‐band (11.424 GHz) electron linear accelerator and YAG laser at Nuclear Engineering Research laboratory, University of Tokyo. This work is a part of the national project on the development of advanced compact medical accelerators in Japan. National Institute for Radiological Science is the host institute and U.Tokyo and KEK are working for the X‐ray source. Main advantage is to produce tunable monochromatic hard (10–80 keV) X‐rays with the intensities of 108–1010 photons/s (at several stages) and the table‐top size. Second important aspect is to reduce noise radiation at a beam dump by adopting the deceleration of electrons after the Compton scattering. This realizes one beamline of a 3rd generation SR source at small facilities without heavy shielding. The final goal is that the linac and laser are installed on the moving gantry. We have designed the X‐band (11.424 GHz) traveling‐wave‐type linac for the purpose. Numerical consideration by CAIN code and luminosity calculation are performed to estimate the X‐ray yield. X‐band thermionic‐cathode RF‐gun and RDS(Round Detuned Structure)‐type X‐band accelerating structure are applied to generate 50 MeV electron beam with 20 pC microbunches (104) for 1 microsecond RF macro‐pulse. The X‐ray yield by the electron beam and Q‐switch Nd:YAG laser of 2 J/10 ns is 107 photons/RF‐pulse (108 photons/sec at 10 pps). We design to adopt a technique of laser circulation to increase the X‐ray yield up to 109 photons/pulse (1010 photons/s). 50 MW X‐band klystron and compact modulator have been constructed and now under tuning. The construction of the whole system has started. X‐ray generation and medical application will be performed in the early next year.